The Bering Sea—A dynamic food web perspective

The Bering Sea is a high-latitude, semi-enclosed sea that supports extensive fish, seabird, marine mammal, and invertebrate populations and some of the world's most productive fisheries. The region consists of several distinct biomes that have undergone wide-scale population variation, in part due to fisheries, but also in part due to the effects of interannual and decadal-scale climatic variation. While recent decades of ocean observation have highlighted possible links between climate and species fluctuations, mechanisms linking climate and population fluctuations are only beginning to be understood. Here, we examine the food webs of Bering Sea ecosystems with particular reference to some key shifts in widely distributed, abundant fish populations and their links with climate variation. Both climate variability and fisheries have substantially altered the Bering Sea ecosystem in the past, but their relative importance in shaping the current ecosystem state remains uncertain.     

Trichodesmium erythraeum (Ehrenberg) bloom along the southwest coast of India (Arabian Sea) and its impact on trace metal concentrations in seawater

The incidence of a large scale Trichodesmium erythraeum bloom along the southwest coast of India (Arabian Sea) observed in May 2005 is reported. Around 4802 filaments of T. erythraeum ml⁻¹ seawater was observed and a colony consisted of 3.6 × 10⁵ cells. The bloom was predominant off Suratkal (12° 59′N and 74° 31′E) with a depth of about 47 m, covering an area of 7 km in length and 2 km width. The concentrations of Zinc, Cadmium, Lead, Copper, Nickel and Cobalt were determined in samples collected from the bloom and non-bloom sites using stripping voltammetry. The observed hydrographical and meteorological parameters were found to be favorable for the bloom. The concentrations of Zinc, Cadmium and Nickel were found to be higher at bloom stations, while the concentrations of Lead, Copper and Cobalt were found to be very low at bloom stations. Elevated concentrations of Cadmium and Cobalt were observed at Valappad mainly due to the decomposition of detrital material produced in the bloom. Statistically significant differences (P > 0.01) in metal concentrations between the bloom and non-bloom stations were not observed except for Copper. Metals such as Lead, Copper and Cobalt were removed from the seawater at all places where bloom was observed. Cadmium was found to be slowly released during the decaying process of the bloom.     

Organic matter origin and distribution in suspended particulate materials and surficial sediments from the western Adriatic Sea (Italy)

In this study, organic carbon (OC), total nitrogen (TN), stable carbon isotopic (δ¹³C_OC) and CuO reaction product compositions were used to identify the sources of organic matter (OM) and to quantify the relative importance of allochthonous and autochthonous contributions to the western Adriatic Sea, Italy. Suspended particulate material (195 samples) and surficial sediments (0–1 cm, 70 samples) from shallow cross-shelf transects were collected in February and May 2003, respectively. Vertical water column profiles were acquired along the same transects. Data include depth, potential temperature, salinity, density and chlorophyll fluorimetry.Along the western Adriatic shelf in the near-shore region, the phytoplankton growth was influenced by dynamics of the buoyant plumes from the Po and Appennine rivers. A small amount of very fine terrigenous material remained suspended within the coastal current and was exported southward along the shelf to the slope. High variability in the bulk composition was detected in the Po prodelta surficial sediments, whereas the western Adriatic shelf, although a larger area, exhibited a narrower range of values.A significant decoupling was observed between suspended particles in the water column and surficial deposits. The organic material collected in the water column was compositionally heterogeneous, with contributions from marine phytoplankton, riverine–estuarine phytoplankton and soil-derived OM. Frequent physical reworking of surficial sediments likely leads to the efficient oxidation of marine OC, resulting in the observed accumulation and preservation of refractory soil-derived OC delivered by the Po and Appennine rivers.     

Application of LICOM to the numerical study of the water exchangebetween the South China Sea and its adjacent oceans

1 IntroductionThe South China Sea (SCS) is the largestmarginal sea in the western Pacific (see Fig. 1). It con-nects with the SCS through the Taiwan Strait, with thePacific through the Luzon Strait, with the Sulu Seathrough the Mindoro and Balabac Straits and with theJava Sea and Andaman Sea through the Sunda Shelf(For convenience, here we refer to the section at 1.5°N,Fig. 2). It is shown that the seasonal SCS circulation ismostly affected by the summer/winter monsoon, andthe no…     

Seasonal and Spatial Variations of Total Mass Flux around Coral Reefs in the Southern Ryukyus,Japan

Total mass flux, size distribution of sediment particles and some chemical components such as total carbon (TC), total nitrogen (TN) and calcium carbonate (CaCO₃) were monitored monthly using a multi-cup sediment traps at seven coral reef sites (6 reef flat and 1 reef slope) of the Marine Protected Areas around Ishigaki, Kohama, Kuroshima and Iriomote Islands in the southern Ryukyus, Japan from September 2000 to September 2001. The size distribution of trapped sediments revealed mostly uni-modal fine sand to mud in the reef flat and gravelly to coarse sand in the reef slope. The total mass flux ranged between 0.54 to 872 gm⁻²d⁻¹, and showed a pronounced seasonality (high in summer-autumn and low in spring) at each site, which was consistent with the rainfall and typhoon regime. Exceptionally high values were observed on the reef slope (Iriomote) in February–March 2001 (1533 gm⁻²d⁻¹) owing to a large amount of bottom sediment re-suspension. On the reef flat (Todoroki South and North; Ishigaki), values obtained in July–August 2001 (872 gm⁻²d⁻¹) and August–September 2001 (800 gm^{− 2}d⁻¹) indicate the high terrestrial discharge from Todoroki River. Trapped sediment particles consist of CaCO₃ (1.2–27.1%) and a non-carbonate fraction (98.8–72.9%), which contains total carbon (4.9–26%), carbonate carbon (CO₂-C) (0.2–3.1%) and non-carbonate carbon (NC-C) (7.9–25.6%). Total nitrogen content was in the range 0.02–0.48%. TN is contained mainly in the carbonate fraction and NC-C may be contained in the non-carbonate fraction. The low TN/OC ratio of the trapped sediments suggests that they were mostly of terrestrial origin and that both fractions migrated. The high total mass flux derived from Todoroki River exceeded the threshold at which a lethal effect on coral community is caused. The results stress the importance of conducting seasonal studies of sedimentation over more than one year and at more than one location in south Japan coral reef ecosystems to gain an understanding of the processes controlling the total mass fluxes and their nutrients content, also to develop an awareness of how to prevent the damage of coral reef ecosystems and, if it does occur, to allow mitigation measures to be undertaken.     

Growth and gonad production of the sea urchin Hemicentrotus pulcherrimus in the fucoid bed and algal turf in northern Japan

To clarify the differences in the growth and gonad size of the sea urchin Hemicentrotus pulcherrimus among algal sere, the study was conducted in June and July, and September 1998 at three fucoid beds in Oga and at three algal turfs in Hachimori, Akita Prefecture in northern Japan. The most rapid growth was observed in a large perennial fucoid bed at the climax stage. Growth in a small perennial Chondrus ocellatus‐dominated bed in algal turfs in the seral stage was then high. The slowest growth was observed in the small perennial Dictyopteris divaricata‐ and Laurencia spp.‐dominated beds which are known to possess chemicals which act as feeding deterrents against the sea urchins. The gonad index (gonad wet weight × 100/body wet weight) at a fucoid bed was high where standing crops exceeded 3 kg·m^?2. The gonad index in the Laurencia bed was lower than those at fucoid beds. These results suggest that growth and gonad production are affected by algal sere and differ among species of small perennial algae in the seral stage with or without chemical defense.     

台湾海峡纽形动物初报

首次报道台湾海峡产的纽形动物，包括沙栖原细首纽虫、浮游拟脑纽虫、椒状岩田纽虫、中华平裂纽虫和马顿氏潘丁纽虫，共５种。除椒状岩田纽虫在琉球群岛有报道外，均为东海新记录。     

北黄海沉积物中重金属分布及环境背景值

本文讨论了北黄海１１个柱状岩芯样的颗粒物（＜０．０６３ｍｍ）中重金属的分布，采用统计学方法对Ｃｕ，Ｐｈ，Ｚｎ和Ｃｄ进行态性检验，用柱样稳定段（拐点以下）作为背景段，获得重金属环境背景值．     

Geophysical Evidence of a Relict Oceanic Crust in the Southwestern Scotia Sea

The southwestern part of the Scotia Sea, at the corner of the Shackleton Fracture Zone with the South Scotia Ridge has been investigated, combining marine magnetic profiles, multichannel seismic reflection data, and satellite-derived gravity anomaly data. From the integrated analysis of data, we identified the presence of the oldest part of the crust in this sector, which tentative age is older than anomaly C10 (28.7 Ma). The area is surrounded by structural features clearly imaged by seismic data, which correspond to gravity lows in the satellite-derived map, and presents a rhomboid-shaped geometry. Along its southern boundary, structural features related to convergence and possible incipient subduction beneath the continental South Scotia Ridge have been evidenced from the seismic profile. We interpret this area, now located at the edge of the south-western Scotia Sea, as a relict of ocean-like crust formed during an earlier, possibly diffuse and disorganized episode of spreading at the first onset of the Drake Passage opening. The successive episode of organized seafloor spreading responsible for the opening of the Drake Passage that definitively separated southern South America from the Antarctic Peninsula, instigated ridge-push forces that can account for the subduction-related structures found along the western part of the South Scotia Ridge. This seafloor accretion phase occurred from 27 to about 10 Ma, when spreading stopped in the western Scotia Sea Ridge, as resulted from the identification of the marine magnetic anomalies.